Clostridium difficile most often strikes the elderly, many of whom are frail and, hence, more susceptible to its bacteria.

The average age of U.S. patients hospitalized with C. diff is 68, meaning that most of the bills are covered by Medicare. With the average cost of a C. diff hospital stay pegged at $24,000, the infection is helping drive up Medicare costs nationally.

Medicare has noticed.

Starting in January, Medicare will start collecting hospitals' C. difficile rates across the United States as part of a new program under the 2010 Affordable Care Act.

In 2015, Medicare will begin using those numbers to judge which hospitals to penalize for not improving their C. difficile rates. Those numbers will be public, and consumers can use them to choose among local hospitals.

That prospect has put even more pressure on hospital employees to determine whether patients are afflicted, cure them, and rein in future infections within their walls.